segmentation fault(coredump)

I think that I have the definition of segmentation fault covered and why other people are receiving this error when I checked on past posts. However, I have no idea why Im getting it....can someone help! Thanks in advance!!!

Code:

---

program7.c

#include "program7.h"

int main(int argc, char *argv[])
{
  char **StringList;
  int i, num, length;

  if (argc != 3)
    printf("Insufficient arguments\n");

  num = atoi(argv[1]);
  length = atoi(argv[2]);

  StringList = (char **)calloc(num, sizeof(char *));

  srand(time(NULL));

  for (i = 0; i < num; i++){
      StringList[i] = RandomString(length);
  }
  printf("Unsorted array:%s\n", StringList[i]);

  /*StringSort(num, StringList)*/
  /*printf("Sorted array:%s\n", StringList[i];
  /*4*/

  return 0;
}

****************************************************

RandomString.c

#include "program7.h"

char *RandomString(int length){

  int i, size;
  char *string;

  size = 1 + rand() % length;

  string = (char *)calloc(size + 1, sizeof(char));

  for(i = 0; i < size; i++){
    string[size] = (char)((rand() % 26) + 65);
  }
  string[size] = '\0';

  return string;

} /* End of RandomString function */

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which compiler are you using?

Im using the cc compiler on UNIX system.

Print from inside the loop, not after i is beyond memory you own.

Code:

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  for (i = 0; i < num; i++){
      StringList[i] = RandomString(length);
      printf("Unsorted array:%s\n", StringList[i]);
  }

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Use your loop index instead of writing everything to the last character and then erasing it.

Code:

---

  for(i = 0; i < size; i++){
    string[i] = (char)((rand() % 26) + 'A');
  }
  string[i] = '\0';

---

Holy $h--, it worked....Thanks a lot Dave, I've been working on that for a long, long time!!!

What if I wanted to put each of those strings in dictionary order?
i.e.
string[1] = dog
string[2] = dogo
string[3] = efgjoz
string[4] = ijs
...
The below code doesnt work and I have been trying to modify it, but no such luck! Any more suggestions?

Code:

---


#include "program7.h"

void StringSort(int num, char *StringList){

  int i, j, temp;

  for(i = 0; i < num; ++i){
    for(j = num; j >= i; --j){
      if(StringList[j - 1] < StringList[j])
        temp = StringList[j - 1];
      StringList[j - 1] = StringList[j];
      StringList[j] = temp;

    } /* End of 1st for statement */

  } /* End of 2nd for statement */

} /* End of StringSort function */

---

Quote:

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Originally posted by chauncey005

Code:

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  if (argc != 3)
    printf("Insufficient arguments\n");

---

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If you are testing for "Insufficient arguments", why do you continue merrily on your way and process the code anyway? You should test for the error and exit, shouldn't you?

Good point, Walt! Thanks for showing me that...I wouldnt have even noticed it!

An adaptation of this:

Code:

---

void StringSort(int num, char **StringList)
{
  int i, j;
  for ( i = (num - 1); i >= 0; i-- )
  {
      for ( j = 1; j <= i; j++ )
      {
        if ( strcmp(StringList[j - 1], StringList[j]) > 0 )
        {
            /* 'previous' is bigger than 'next' -- swap pointers */
            char *temp        = StringList[j - 1];
            StringList[j - 1] = StringList[j];
            StringList[j]    = temp;
        }
      }
  }
}

---

Thank you, I can generate the random strings and I tried the code for the StringSort below, however, when I try to sort them I am now receiving the error: segmentation fault(coredump). Ive tried resituating the code as was the case before, but that doesnt work. Any more ideas anyone? Thank you again!

The following was my "putting it all together" test code.

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

char *myrandstr(int length)
{
  int i, size = 1 + rand() % length;
  char *word = malloc((size + 1) * sizeof *word);
  if ( word )
  {
      for ( i = 0; i < size; i++ )
      {
        word[i] = (char)((rand() % 26) + 'A');
      }
      word[i] = '\0';
  }
  return word;
}

/* http://linux.wku.edu/~lamonml/algor/sort/bubble.html */
void mystrsort(int num, char **word)
{
  int i, j;
  for ( i = (num - 1); i >= 0; i-- )
  {
      for ( j = 1; j <= i; j++ )
      {
        if ( strcmp(word[j - 1], word[j]) > 0 )
        {
            char *temp  = word[j - 1];
            word[j - 1] = word[j];
            word[j]    = temp;
        }
      }
  }
}

int main(int argc, char *argv[])
{
  if ( argc == 3 )
  {
      int i, num = atoi(argv[1]), length = atoi(argv[2]);
      char **word = malloc(num * sizeof *word);
      if ( word )
      {
        srand(time(NULL));
        /*
          * Make a list and print it.
          */
        puts("---Unsorted---");
        for ( i = 0; i < num; i++ )
        {
            word[i] = myrandstr(length);
            puts(word[i]);
        }
        /*
          * Sort it and print it.
          */
        mystrsort(num, word);
        puts("----Sorted----");
        for ( i = 0; i < num; i++ )
        {
            puts(word[i]);
        }
        /*
          * Clean up.
          */
        for ( i = 0; i < num; i++ )
        {
            free(word[i]);
        }
        free(word);
      }
  }
  return 0;
}

/* my output
C:\test>test 5 10
---Unsorted---
KXMFKFPRXT
LQEPET
S
IIIAPLFWR
MAJZMF
----Sorted----
IIIAPLFWR
KXMFKFPRXT
LQEPET
MAJZMF
S
*/

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That works, but unfortunately we cant use strcmp() or puts()...but thanks anyways!

>but unfortunately we cant use strcmp() or puts()...
strcmp is trivial to write, and puts functionality can be simulated with printf (not to mention that puts was used to test that the function worked so that you would get correct code). You should be a little more considerate when someone posts a largish chunk of code that was written just for your benefit.